The reason given in Briffa 2001 for their selection of a certain reconstruction is discussed: >> > The selection of a single reconstruction of the ALL temperature series is clearly somewhat arbitrary... The method that produces the best fit in the
calibration period is principal component
regression... << >> ``... we note that the 1450s were much cooler in all of the other (i.e., not PCA
regression) methods of producing this
curve...» << <
The
curved blue lines in Figure 9 - 1 present the
calibration error, or the uncertainty in predictions based on the
calibration (technically the 95 percent prediction interval, which has probability 0.95 of covering the unknown temperature), which is a standard component of a
regression analysis.